Clarify initial value of [[SegmentIteratorBreakType]] about proposal-intl-segmenter

[FrankYFTang]

I also think this is very confusing especially when the granularity is GRAPHEME . Should CreateSegmentIterator then set it to undefined (which is not a string)? or a different string?

[littledan]

I agree, the initial value should be undefined. PRs welcome, or I'll write one if no one else does.

Beyond that, the implementation-defined nature is defnitely confusing. I was intending that this could be a member of ICU's type enum, but I wasn't sure how to indicate that (I don't see these semantics anywhere in Unicode/CLDR). The big application that I'm aware of for this property is, when breaking lines, to tell between a hard and soft line break, and when breaking words, to tell whether we're starting whitespace or starting another word. Do you have any particular idea for how we should present this aspect of the API?

[littledan]

Oh, I forgot about how we actually did define the break types in the break type table, heh. I guess the change needed is to set it to undefined. Sorry for getting so confused above.

[FrankYFTang]

your changes in #41 address it will. The issue is "string" vs "value". Using the word "value" is surely much better on those part of spec. Thanks!